This invention relates to a radiation sensitive resin composition. More particularly, it relates to a radiation sensitive resin composition which is useful as a resist particularly suitable for fine processing using a radiation such as ultraviolet rays (e.g. UV), deep ultraviolet rays (e.g. deep UV), X rays or charged particle beams.
In the field of fine processing, a representative of which is the production of an integrated circuit device, the fining of the processing size in lithography is now proceeding quickly in order to obtain a higher integration degree of integrated circuit, and development of a lithographic processing which enables fine processing to be conducted stably with such a high precision that line widths of halfmicron or less are now pushed ahead. However, in a conventional method in which visible light (wavelength: 700-400 nm) or near ultraviolet light (wavelength: 400-300 nm) is used, it is difficult to form such a fine pattern with a high precision, and hence, there has been proposed a lithographic process which can achieve a wider depth of focus and uses a shorter radiation wavelength (wave-length: 300 nm or less) which is effective to the fining of design rule.
As a lithographic process using such short wavelength radiation, there has been proposed a process using deep UV such as KrF excimer laser (wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm) or the like; X rays such as synchrotron radiation or the like; or charged particle beams such as electron beams or the like. As a high resolution resist corresponding to such a short wavelength radiation, a chemically amplified resist has been proposed by INTERNATIONAL BUSINESS MACHINES CORPORATION (IBM), and improvement and development of this chemically amplified resist are now being energetically developed.
In the case of such a chemically amplified resist, such a phenomenon that the radiation sensitive acid generator contained therein generates an acid upon irradiation with a radiation (the irradiation is referred to hereinafter as the exposure), and the catalytic action of this acid causes a chemical reaction in a resist coating film (for example, change of polarity, cleavage of chemical bond, crosslinking reaction or the like), whereby the solubility of the exposed portion in a developer is changed, is utilized to form a pattern.
As those chemically amplified resists which show relatively good resist performance, there are known, for example, those containing, as a resin component, an alkali-soluble resin having an alkali affinity group protected with a tert-butyl ester group or a tert-butoxycarbonyl group (for example, Japanese Patent Application Kokoku No. 2-27,660); an alkali-soluble resin having an alkali affinity group protected with a silyl group (for example, Japanese Patent Application Kokoku No. 3-44,290); a resin containing a (meth)acrylic acid component (for example, Japanese Patent Application Kokai No. 4-39,665), a mixture of such a resin with a phenolic novolak resin (for, example, Japanese Patent Application Kokai No. 63-250,642) and the like. However, it has been pointed out that these chemically amplified resists have respective inherent problems and various difficulties accompany putting the resists to practical use.
That is to say, in the system in which a resin having a tert-butyl ester group or a tert-butoxycarbonyl group is used, the chemical reaction based on the catalytic action of the acid generated upon the exposure is accompanied by the liberation of a gas component such as an isobutene gas or a carbon dioxide gas, so that volume shrinkage is caused in the exposed portion, and consequently, the pattern profile tends to be distorted and hence the formation of a high precision resist pattern is difficult. In the case of a resist in which a resin having a silyl group is used, the pattern profile is generally good; however, there is such a disadvantage that it is inferior in peelability from a substrate to a resist using a silyl group-free resist. In addition, where a (co)poly(meth)acrylic acid as a resin is used, there is such a problem the adhesiveness between the resist and the substrate of silicon and the like is insufficient and the dry etching resistance is lower than that of a resist using an aromatic resin (for example, a phenol novolak resin or the like) as a constituent resin of resist.
In order to solve the above-mentioned problems in the chemically amplified resists, resins having both (meth)acrylic acid ester unit and phenol skeleton have recently been proposed and attention is directed thereto (see, for example, Japanese Patent Application Kokai Nos. 4-251,259; 5-181,279 and 5-113,667). However, in the case of these resists, the dry etching resistance is improved; however, a good rectangular pattern is difficult to obtain and there is a problem in respect of pattern profile. Moreover, said resists are insufficient in resolution, developability and the like and a further improvement of said resists is desired from the viewpoint of collective characteristics of chemically amplified resists.